Effect of solvents on the chiral recognition mechanisms of immobilized cellulose-based chiral stationary phase.

The effect of solvents on the enantioselectivities of four structurally similar chiral solutes with a cellulose derivative-based chiral stationary phase, Chiralpak IB, were studied using acetone (AC), 2-propanol (IPA), and tert-butanol (TBA) separately as polar modifiers. The enantioselectivities α of benzoin and methyl mandelate decrease with an increase in modifier concentration CM, whereas the enantioselectivity of pantolactone increased with increasing AC concentration. These results were attributed to the heterogeneous adsorption mechanisms of enantiomers. To interpret the dependence of enantioselectivity on modifier content, an enantioselectivity model based on a two-site adsorption model was proposed. The dependence of α on CM was inferred to be mainly due to the distinct modulating effects of modifier concentration on the two adsorption sites: the nonselective type-I site and enantioselective type-II site. The model fitted the benzoin data satisfactorily over a wide TBA concentration range. The retention factors as a function of TBA concentration were successfully deconvoluted for each site. With the use of the proposed model, it was inferred that the chiral recognitions of benzoin and methyl mandelate were mainly achieved by the presence of an aromatic group adjacent to the hydroxyl group. When using IPA and TBA separately as modifiers, the presence of an aromatic group adjacent to the ketone group mainly contributed to the nonselective π interactions and enantioselective steric interactions, respectively. These results, along with those of the modifier adsorption isotherms, determined using the perturbation method, as well as the retention behaviors of various achiral solutes, indicate that the molecular recognition mechanism of IB sorbent is highly sensitive to the adsorbate's molecular geometry. The molecular environment of the sorbent can be controlled using different modifiers, leading to distinct adsorption and retention mechanisms.

Long-Term Effect against Methicillin-Resistant Staphylococcus aureus of Emodin Released from Coaxial Electrospinning Nanofiber Membranes with a Biphasic Profile.

Methicillin-resistant Staphylococcus aureus (MRSA) is a serious and rapidly growing threat to human beings. Emodin has a potent activity against MRSA; however, its usage is limited due to high hydrophobicity and low oral bioavailability. Thus, the coaxial electrospinning nanofibers encapsulating emodin in the core of hydrophilic poly (vinylpyrrolidone), with a hygroscopic cellulose acetate sheath, have been fabricated to provide long-term effect against MRSA. Scanning electron microscopy and transmission electron microscopy confirmed the nanofibers had a linear morphology with nanometer in diameter, smooth surface, and core-shell structure. Attenuated total reflection-Fourier transform infrared spectra, X-ray diffraction patterns, and differential scanning calorimetric analyses verified emodin existed in amorphous form in the nanofibers. The nanofibers have 99.38 ± 1.00% entrapment efficiency of emodin and 167.8 ± 0.20 % swelling ratio. Emodin released from nanofibers showed a biphasic drug release profile with an initial rapid release followed by a slower sustained release. CCK-8 assays confirmed the nontoxic nature of the emodin-loaded nanofibers to HaCaT cells. The anti-MRSA activity of the nanofibers can persist up to 9 days in AATCC147 and soft-agar overlay assays. These findings suggest that the emodin-loaded electrospun nanofibers with core-shell structure could be used as topical drug delivery system for wound infected by MRSA.

Comprehensive analysis of the compound profiles of Folium Camelliae Nitidissimae extract by ultrafast liquid chromatography with quadrupole-time-of-flight mass spectrometry and hepatoprotective effect against CCl4 -induced liver injury in mice.

Folium Camelliae Nitidissimae (jinhuacha in Chinese, JHC) is a kind of caffeine-less tea with antioxidant, antitumor and antibacterial effects. Studies on the chemical profiles and hepatoprotective effects of JHC extracts have not been systematically conducted so far. This study comprehensively investigated the compound profiles of JHC extract by ultrafast liquid chromatography with quadrupole time-of-flight tandem mass spectrometry. We also determined JHC's hepatoprotective effects against CCl4 -induced liver injury in mice. A JHC extract was administered orally to mice at 1.95 and 7.80 g/kg body weight once daily for 14 consecutive days prior to CCl4 treatment. Eighty-four compounds including flavonoids, organic acids, catechins, coumarins, phenylpropanol, amino acids, anthraquinones, saponins and nucleosides in JHC extract were authentically identified or tentatively identified by comparing MS information and retention times with those of authentic standards or available references. JHC administration significantly decreased elevated levels of aspartate aminotransferase and alanine aminotransferase in mouse serum, inhibited hepatic malondialdehyde formation and enhanced glutathione and superoxide dismutase activities in the liver of CCl4 -treated mice. The histological observations also further supported the results. These results demonstrate that JHC contains various chemical compounds and its hepatoprotective effects against CCl4 -induced liver injury correlated with decreasing lipid oxidation are significant.